Lol. So mine comes out to .835

 

Seems pretty high, the rule of thumb is 0.6-0.65 IIRC. Perhaps we are shooting for lower AFRs than what the rule of thumb implies.

 

How did either of you tune for the meth?

 

Thats really what I am curious about...where did that rule of thumb come from? What assumptions were absorbed into that?

Eric, when I was on the dyno I didnt have meth on at the time, but in general I shoot for a couple point drop in lambda and consistency through the rpm range by adjusting the boost ramp rate.

 

Always rules of thumb...often never correct lol. I tune for meth the same way, Richard.

 

IMO, the way to tune for meth is to correct the non-meth tune while meth is running (e.g. pull fuel with meth running to get the AFR into the range you want it -- for instance Atomic runs at .8 lambda or 11.75 AFR : that should still be your target as you are still running primarily a gasoline engine). The downside is, of course, if your meth fails, your engine will pop. Running very rich also has a downside -- destroying the ring seal, and possible damage from cleaning the oil out of the cylinder.

OW, you are running significantly rich, depending on meth usage. Meth will skew AFR significantly richer (around 25% in my experience). That could definitely explain your significantly high BSFCs.

I would hazard a guess that the rule thumb mentioned above is using a 'ragged edge' drag racing inspired AFR target (like 12-12.5 for a turbo). Personally, I target 11.5 a street vehicle. I personally think turbos should have a rule of thumb that indicates a BSFC of .60 or higher due to the extreme boost levels that can be made. There is no way someone running 6 psi will have anywhere close to the BSFC of someone running 26psi (just think of the VE changes from an additional 20psi).

BTW, if I understood you two correctly, you shoot for .8 lambda and allow for a .6 with meth running? That would be a sub 9 AFR -- waaaaaay too rich IMO.

 

Looking at it another way, a BSFC of .78 means you are using .78 lbs of fuel per hour for each HP you are making (assuming bhp here). Given your 127s at .95 yield around 965.2 lbs per hour, that would mean you are producing around 1237 at the crank (ignoring the meth).

 

No, my meth tunes end up a tad richer but not much. Maybe a third of a point richer on the AFR scale. Then again, I haven't tuned multiple nozzles yet, I'm a slacker...haven't run my new meth kit yet. Richard, what did you mean by couple point drop..?

 

I shoulda mentioned I run multiple nozzles and a lot of gain

 

Yea, which sounds about right...

by a few points I mean 0.01-0.05 lambda. So If I tune it for 0.8 lambda on gas only itll be around .76-.78 with meth.